Dismountable pressure pump



May 4, 1965 R. A. YOHPE DISMOUNTABLE PRESSURE PUMP 2 Sheets-Sheet 1 Filed June 4, 1962 HM mm mm mill MI W! Ml 1%. W w A y 4, 1965 R. A. YOHPE 3,181,474

DISMOUNTABLE PRESSURE PUMP Filed June 4, 1962 2 Sheets-Sheet 2 INVENTOR Jam/11m BY 419M ORNEY 3,131,474 i atentecl ay 4, 1965 3,181,474 DISMOE 1N IABLE PdURE PUMP Reinhard A. Yohpe, Battle Creek, Mich, assignor to Union Pump Company, Battle Creek, Mich, a corporation of Michigan Filed June 4, 1962, Ser. No. 199,779 9 Claims. (Cl. 103-153) This invention relates to pumps and, in particular, to a high pressure pump of the reciprocating type adapted to be employed for pumping food materials, as in homogenizers for various dairy products, and which may be readily disassembled for cleaning and sterilizing purposes and then readily reassembled.

While the pump of the present invention may be utilized to advantage in various environments, it has been particularly developed for use in the high pressure pumping of food products, and particularly as a component of an apparatus for homogenizing dairy products, and thus requiring frequent disassembly of various components of the pump for the purpose of cleaning and sterilizing them for sanitary purposes, followed by subsequent reassembly of the pump. Accordingly, in order to facilitate an understanding of the invention and the significance thereof, reference will be made hereinafter to various problems heretofore presented and overcome by the present invention to the art of pumping dairy and other food products at high pressures although, as aforementioned, the present invention has other applications which will become readily apparent to those acquainted with the pump art.

High pressure pumps of the type typically employed for pumping food products, such as in a homogenizing apparatus for various dairy products, must as aforemen tioned be disassembled quite frequently for the purpose of cleaning and sterilizing the various components thereof for sanitary purposes. To this end, such pumps have typically comprised a housing or cylinder block enclosing a pumping chamber, and which housing has comprised oppositely spaced walls in one of which a pump plunger has been suitably mounted for reciprocation under the influence of a suitable external source of power. Inlet and outlet passage means including, respectively, inlet and outlet valve means have been provided in the housing in communication with the aforementioned pumping chamber. A valve cover has been associated with the outlet passage means and the outlet valve disposed therein for access to the latter for cleaning purposes, while the wall of the housing or cylinder block opposite the pump plunger has been bored to removably receive a closure member permitting access to the pumping chamber for removal of the pump plunger as well as the inlet valve means.

As will be apparent, it has been necessary that the diameter of the access bore aforementioned be sufficiently larger than the diameter of the pump plunger to permit the latter to be removed and inserted therethrough as well as the aforementioned inlet valve means and, in the instances inwhich a cylinder sleeve has been disposed within the pumping chamber of the housing to receive the plunger, sufficiently large enough to accommodate removal and insertion of such a sleeve. This, of course, has necessitated using a cylinder block or housing of suifcient height to accommodate a bore of the required size and the various passageways and valving associated therewith and, further, unless associating a cylinder sleeve or the like with the pump plunger, has resulted in a relatively large volumetric clearance for the pump plunger within the pumping chamber which deleteriously affect priming of the pump, and results in some volatilization and vapor binding when pumping volatile liquids thereby decreasing volumetric efficiency of the pump. Further, since volatile liquids usually have appreciable compressibility at high pressures, the aforementioned clearance volumes found in prior pumps for the reasons aforementioned likewise oontribte to a decrease in the volumetric efficiency of the pump.

In addition, the size requirement for such an access bore to the pumping chamber of such a pump has resulted in a correspondingly large closure member therefore presenting a working area opposite the working face :of the pump plunger against which an elfective hydraulic force acts in response to the high pressure pumping action of the plunger. As a consequence, the pump housing, and particularly the wall thereof to which the closure member is removably attached, and the closure member itself have been of relatively thick and heavy construction and relatively heavy-duty studs, or a great number thereof, have been required to accommodate such large hydraulic forces. Furthermore, in a pump mechanism of this type normally employed with homogenizing equipment for dairy products, usually three pump assemblies each including a reciprocating pump plunger and closure member opposite thereto are normally disposed side-by-side within a cylinder block or housing, and the spacing between such pump assemblies is determined, among other things, by the space required along a wall of the housing for attachment of the closure members thereto. Accordingly, where relatively large and heavy closure members and large or many securing studs therefor are required as in the prior art, the spacing between pump assemblies may be relatively great, thereby further contributing to the overall size and cost of the pump mechanism and particularly the housing or cylinder block thereof. In addition, the heavy closure members required in prior assemblies of this type have not particularly contributed to the ease of handling and cleaning thereof.

In view of the foregoing considerations, the present invention includes among its objects the provision of an improved pump comprising a housing or cylinder block including a pumping chamber therein, a pump plunger reciprocably mounted through one wall of the housing for reciprocationwithin the pumping chamber, a cylindrical access bore in an opposite wall of the housing for access to the interior of the housing and the pumping chamber therein for assembly and disassembly of an inlet valve means and the pump plunger therethrough, and a closure member for such access bore removably mountable therein, and characterized by the fact that the axis of the access bore is eccentric to the axis of the pump plunger to contribute to a reduction in the size of the pumping chamber and consequent reduction in the size of the housing and increased volumetric efiiciency and ease of priming of the pump.

it is yet another object and feature of this invention to provide a pump of the type aforementioned in which the closure member removably mountable within the eccentric access bore is smaller in diameter than the universally used concentric closure member, thus minimizing the effective hydraulic force applied against the closure member, thereby enabling the use of a housing and closure member of smaller size and Weight and attaching studs or the like therefor of smaller size, or a fewer number thereof, which materially contributes to diminishing the overall size of the assembly, its weight and cost, and further facilitates handling of various parts of the pump assembly and particularly the lighter closure member during disassembly, cleaning, and assembly thereof.

It is yet another object and feature of this invention to provide a pump of the type aforementioned further characterized by an inlet passage means including inlet valve means disposed substantially at a right angle to the the aforementioned closure member having the army means projecting therefrom, in which the arm means includes an arcuately curved surface substantially concentric with the pump plunger and immediately adjacent thereto and at the inlet valve side of same, with the access bore being eccentric and positioned so that the outlet valve side of same will closely but freely permit withdrawal of the pump plunger through said bore while allowing the use of a relatively small closure member,

thereby reducing the eflfective total hydraulic force applied to the closure member while utilizing an access bore of sufiicient size to permit ready assembly and disassembly of pump components therethrough.

It is yet another object and feature of this invention to provide a pump of the type aforementioned particularly adapted to be combined in multiple groups thereof, as in homogenizing equipment for dairy products, whereby the afore-mentioned reduction in hydraulic forces and consequent reduction in size in the closure members and fastener means therefor associated with each access bore of each pump permit the-pumps to be mounted closer to each other center-to-center, thereby further contributing to an overall diminishing in the size of the entire pump mechanism, and consequently its weight and cost.

Still further objects, features and advantages of the invention will appear hereinafter as the description of the invention proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims, the annexed drawings and the following description setting forth in detail certain means for carrying out the invention, such disclosed means illustrating, however, but one of the various ways in which the principle of the invention may be used;

In the annexed drawings: 7

FIGURE 1 is a side elevation of a pump mechanism illustrating a preferred embodiment of this invention; FIGURE 2 is an elevational view taken from the other side of the pump mechanism of FIGURE 1 and partially broken away and in section to illustrate certain details of the invention; and

FIGURE 3 is a sectional view taken on line 3-3 of FIGURE 2.

products; that is, a pump mechanism including three distinct and identical'pump assemblies 12, 14 and 16 contained in a single housing or cylinder block 13 including the opposed wall members 20 and 22. However, and as will become more fully apparent hereinafter, each of the pump assemblies may be used alone and for the purpose other than in homogenizing equipment.

The housing 18 includes an inlet bore or gallery 24 capped at one end, not shown, and provided with a threaded fitting 26 at the other end thereof for connection to the source of fiuid to be'pumped. 'In similar fashion, an outlet bore or gallery 28 is provided in an opposite portion of the housing 18 and is similarly capped at one end and provided at the other end with a threaded fitting 30 adapted to be connected to asuitable discharge receptacle or, in this case, to a'conventional homogenizing valve, not shown. Since each of the pump assemblies 12, 14 and 16 and their respective connections to the aforementioned inlet bore or gallery 2 3 and outlet bore or gallery 28 are identical, it will suffice to describe the details of the pump assembly 12 particularly illustrated in FIGURES 2 and 3 for a complete understanding of the invention.

The pump assembly 12, and each thereof comprises a stuffing box 32 formed integral with or otherwise rigidly secured to and projecting from the wall member 20 and having a cylindrical bore 34 joined through the annular shoulder 3-6 to a cylindrical bore 38 of reduced diameter coaxial with the bore 34. and communicating with the pumping chamber 40 interiorly of the housing 18. Axially inner and outer throat members 42 and 44 are removably slidably disposed within the bore 34 with a packing or seal 4e disposed therebetween, the axially inner throat member 42 being adapted to abuttingly engage the annular shoulder 36. A threaded gland nut 48 is adapted to adjustably threada'oly engage threads carried on the exterior of the stulfing box 32 as indicated in FIGURE 3 and in a known manner to adjust the position ofthe axially outer throat member 44 relative to the inner throat member 42 and packing or seal 46 therebetween in a conventional manner; The annular throat members 42 and 44 are coaxial with the bores 34 and 38, and have equal diameters slightly smaller than the diameter of the bore 38 to slidably support the pump plunger 56 which extends through the gland nut 48 and is equipped with the usual fitting 52 for connection to an external power source for reciprocating the plunger within the pumping chamber 40.

The inlet bore or gallery 234 communicates fluid therein to the pumping chamber 46, and each thereof, through an inlet passage means comprising the inlet bore S4 including a conventional valve seat 56 which may be formed integrally therewith or separable for removal therefrom as will be apparent to those acquainted with this art. A conventional inlet valve member 58 is mounted for guided reciprocation within the valve seat and relative thereto between a position seating on the latter as illustrated in FIGURES 2 and 3 and a position displaced therefrom toward the axis of the pump plunger 5i during a suction stroke of the latter. A stop member 6t) is secured to the inlet valve member 58, and a compression spring 62 surrounds the stop member and has one end engaging the inlet valve member while the other end is enclosed in an inverted cup-shaped retaining cap 64 engageable with a surface of an arm member to be hereinafter described;

' The stop member of is engageable with the retaining cap do to limit movement of inlet valve member 58 from the valve seat, while, 62 provides positive seating action for the inlet valve member.

In similar fashion,'the pumping chamber 4% communicates with the outlet bore or gallery 28 through an outlet passage means comprising the outlet bore 66 including a conventional valve seat 68 which may be formed integrally therewith or separable for removal therefrom as will be apparent to those acquainted with this art. A conventional outlet valve member "iii is mounted for guidedreciprocation within the valve seat and relative thereto between a position seating thereon as illustarted in FIGURES land 3 and a position displaced therefrom away from the axis of the pump plunger to permit fluid to be discharged on a pumping stroke of the pump plunger to the outlet bore or gallery 28. A stop member 72 is secured to the outlet valve member 7% and a compression spring 74 surrounds the stop member and has one end engaging the'outlet valve member 70 and a stop member 76 projecting into the outlet bore 66 from a valve cover 78 including an exterior flange portion suitably secured as by the bolts 80 to the respective wall members 2% and 22 of the housing. Suitable sealing means 82 are provided between valve cover 78 and the outlet bore 66. a The stop member '72 is engageable with stop memebr '76 to limit 'movement of outlet valve member 7t) from the valve seat,

and spring 74 provides positive seating action for the outlet valve member,

means including the inlet bore 54- and inlet valve member 58 and the outlet passage means including the outlet bore 66 and the outlet valve member 70 are substantially axially aligned and disposed substantially at right angles to the axis of the pump plunger 50.

The wall member 22 includes a cylindrical access bore 84 communicating the interior of the housing 18 and the pumping chamber 4t therein exteriorly of the housing to permit assembly and disassembly therethrough of the pump plunger 50, inlet valve member 523, spring 62 and retaining cap 64 as well as valve seat 56, if of the removable variety as illustrated, for cleaning purposes. At this juncture, it is to be noted that the axis of the cylindrical access bore 84 intersects the common axis of the aforementioned inlet and outlet passage means, and is located a predetermined distance eccentrically from the axis of the pump plunger 59 toward the inlet bore 54. Consequently, the radial clearance between the lower portions of the pump plunger 50 and the access bore 84 adjacent the inlet bore 54 as illustrated particularly in FIGURE 2 is a predetermined distance greater than the similar radial clearance between the opposite or upper portions of the pump plunger and access bore adjacent the outlet bore 66. While the radial clearance between the pump plunger and the associated portion of the access bore adjacent the outlet valve bore need only be large enough to avoid interference therebetween, preferably this clearance is slightly greater than the minimum indicated above to allow optimum liquid passage through the outlet bore. The aforementioned radial clearance between the pump plunger and the associated portion of the access bore adjacent the inlet bore 54 is, as aforementioned, greater and, in this regard, suiiiciently greater so as to receive the aforementioned arm member engageable with the retaining cap 64 as will appear hereinafter.

A closure member 36 comprises cylindrical closure plug 88 having a suitable seal 9% in its periphery and re movably receivable within the access bore 84 to close the latter, and includes an arm member 92 projecting from the inner surface Q4 thereof alon its periphery into the pumping chamber 4% so as to be disposed between the path of travel of the pump plunger 5t and the retaining cap 64 which abuts the adjacent surface thereof. As will be apparent from FIGURES 2 and 3, the arm member 92 is arcuately curved in section and includes the arcuately curved surface 96 immediately adjacent the periphery of the pump plunger so and substantially concentric with the axis of the latter. The space between the arcuately curved surface 96 and pump plunger 5th is just sufficient to provide working clearance therebetween. It will also be noted that the length and width of the arm member are both smaller in dimension than the diam eter of the inlet bore 54, thereby permitting iiuid flowing to the pumping chamber to flow around both sides and the end of the arm member. The closure member 36 further includes an elongate flange 98 formed integral with or otherwise rigidly secured to the closure plug $3 and adapted to be rigidly removably secured to the exterior of the wall member 22 of the housing as by the bolts 169.

In operation, it will of course be appreciated that, as the pump plunger 5% is reciprocated within the throat members 42. and 44 and the pumping chamber 40 by the external power source, fluid to be pumped is delivered from the inlet bore or gallery 24 to the pumping chamber 4-9 around the arm member 92 upon unseating of the inlet valve member 53 on a suction stroke of the pump plunger. in this regard, the stop member till is abuttable with retaining cap 54 engaging the arm member 92 to limit radial or upward movement of the inlet valve member 58 in FIGURES 2 and 3 during this suction stroke, the spring 62 operating to positively return the inlet valve member to its seat at the end of thesuction stroke. Fluid so delivered to the pumping chamber is then pumped during a compression stroke of the pump plunger past the outlet valve member which moves off its seat to the extent permitted by engagement of the stop members 72 and 76, with the spring 74- operating to positively return the outlet valve member to its seat at the end of the compression stroke. Fluid so pumped is delivered into the outlet bore or gallery 23 to a suitable receptacle or, in this instance, to a homogenizer valve, not shown.

During this pumping action, and particularly during a compression stroke of the pump plunger 5%, the pressures generated by the working face thereof act against the inner surface of the closure plug 88 which is smaller in area than the area of a closure plug fitting a conventional access opening concentric with the pump plunger. As a consequence, the effective hydraulic force acting on the inner surface 94 of the closure plug 8% is smaller than would be the use if the surface of the closure plug exposed to the working face of the pump plunger were as large as the access bore concentric with the pump plunger as in prior constructions of pumps of this type.

When it is desired to clean and sterilize various of the components of the pump, the studs we and closure member 86 may be removed for access to and removal of pump plunger 50 and the inlet valve construction aforedescribed through the access bore 84. The valve cover 7% may also be removed for access to the outlet valve construction. After the cleaning operation has been completed, the pump plunger 58 may be reinserted through the access bore 84 and the throat members 42 and 44 to the position shown in FIGURE 3 at which time the fitting 52 thereof may be again connected to the external power source. Also, the inlet valve construction may be reinserted through the access bore into the position illustrated particularly in FIGURE 3, and the closure member 86 replaced with the arm member 92. engaging the retaining cap 64 as previously described. In similar fashion, the outlet valve structure may be replaced and the valve cover 78 resecured to the housing.

In view of the foregoing description, it will now be apparent that the present invention contemplates an access bore 84 having an area smaller than the areas of similar bores in prior art pumps for ready assembly and disassembly of pump components therethrough but which, by reason of its eccentric disposition with respect to the axis of the pump plunger 5t and cooperation therewith of closure member 36 including the arm member 92, rcsults in a pump assembly in which the volumetric clearance of the pumping chamber 4% about the pump plunger 5% is minimized, thereby reducing the overall height of the cylinder block or housing 18, providing improved priming of the pump and increased volumetric efficiency thereof as aforementioned. Furthermore, due to the reduction of the total effect of forces imposed upon the inner surface 94 of the closure plug 88 by the pump plunger fill, the thickness of the wall members of the housing may be minimized, as may be the size and weight of the closure member 86 and the studs 1th), or the number thereof, utilized to secure same to the housing. Furthermore, where pump assemblies are utilized in multiple groups as illustrated in the drawings, the reduction in force ap- V plied to the closure members 36 for each of the respective pump assemblies and the consequent reduction in size of the means utilized to attach such closure members to the housing permit closer center-to-center spacing of the pump assemblies, thereby further contributing to a reduction in the overall size, weight and cost of a multiple pump mechanism.

While but one form of the invention has been shown and described, other forms will now be apparent to those skilled in the art. Therefore, it will be understand that the embodiment shown in the drawing and described above is merely for illustrative purposes, and is not intend-ed to limit the spirit and scope of the invention.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed,

provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A fluid pump comprising a housing enclosing a pumping chamber therein, said housing including opposed wall means, pump plunger, means mounting said plunger through one of said wall means for reciprocation within said chamber, inlet passage means communicating with said chamber, means defining an access bore through said other wall means to said chamber, the axis of said bore being located a predetermined distance eccentrically from the axis of said plunger toward said inlet passage means, a closure member removably mountable within said bore, arm means secured to said closure member and projecting therefrom into said chamber between said plunger and said inlet passage means, the width of said arm means being smaller than said inlet passage means whereby fluid flowing therefrom into said chamber may pass around the sides of said arm means, and an outlet passage means communicating with said pumping chamber.

2. Thepump as defined in claim 1 in which said arm means defines with the surface of said closure member exposed to said pumping chamber a working area opposite the end of said plunger which is less than the area of said bore.

. 3. A high pressure fluid pump comprising a housing enclosing a pumping chamber therein, said housing including opposed wall means, a cylindrical pump plunger, means mounting said plunger through one of said wall means for reciprocation within said chamber, inlet passage means including inlet valve means communicating was said chamber, outlet passage means including outlet valve means communicating with said chamber, said inlet and outlet passage means including the respective valve means thereof being substantially aligned on an axis disposed substantially at a right angle to the axis of said plunger, means defining an access bore through said other wall means to said chamber, the axis of said bore intersecting the axis of said inlet and outlet passage means and being located a predetermined distance eccentrically from the axis of said plunger toward said inlet passage means whereby the radial clearance between said plunger and said bore adjacent said inlet passage means is a predetermined distance greater than the radial clearance between said plunger and said bore adjacent said outlet passage means, a closure member removably mountable within said bore, and arm means secured to said closure member and projecting therefrom into said chamber between said plunger and said inlet passage means, the length and width of said arm means being smaller than said inlet passage means whereby fluid flowing therefrom into said chamber may pass around the sides and end of said arm means.

4. The pump as defined in claim. 3 in which said inlet valve means comprises a valve seat within said inlet passage means, an inlet valve member in said inlet passage means and movable between a seated position on said valve seat and an unseated position displaced therefrom toward said pumping chamber, a stop member secured to said valve member and projecting therefrom toward said pumping chamber, a'spring surrounding said stop member and having one end engaging said valve member, and a retaining cap receiving the other end of said spring and engageable with said arm means. i

5. A high pressure fluid pump comprising a housing enclosing a pumping chamber therein, said housing including opposed wall means, a cylindrical pump plunger, means mounting said plunger through one of said wall means for reciprocation within said chamber, inlet passage means including inlet valve means communicating with said chamber, outlet passage means including outlet valve means communicating with said chamber, said inlet and outlet passage means including the respective valve means thereof being substantially aligned on an axis disposed 8 substantially at a right angle to the axis of said plunger, means defining a cylindrical access bore through said other Wall means to said chamber, the axis of said bore intersecting the axis of said inlet and outlet passage means and being located a predetermined distance eccentrically from the axis of said plunger toward said inlet passage means whereby the radial clearance between said plunger and said bore adjacent said inlet passage means is a predetermined distance greater than the radial clearance between said plunger and said'bore adjacent said outlet passage means, a closure member removably mounted within said bore, arm means secured to said closure member and projecting therefrom into said chamber between said plunger and said inlet passage means, the length and width of said arm means being smaller than said inlet passage means whereby fluid flowing therefrom into said chamber may pass around the sides and end of said arm means, and an arcuately curved surface on said arm means adjacent said plunger and substantially concentric with the latter.

6. The pump as defined in claim 5 in which said arcuately curved surface on said arm means defines with the surface of said closure member exposed to said pumping chamber a working area opposite the end of said pump plunger which is less than the area of said bore.

7. The pump as defined in claim 6 in which said inlet valve means comprises a valve'seat within said inlet passage means, an inlet valve member in said inlet passage means and movable between a seated position on said valve seat and an unseated position displaced therefrom toward said pumping chamber, a stop member secured to said valve member and projecting therefrom toward said pumping chamber, a spring surrounding said stop member and having one end engaging said valve member, and a retaining cap receiving the other end of said spring and engageable with a surface of said arm means opposite said arcuately curved surface thereof.

8. A high pressure fluid pump comprising a housing enclosing a pumping chamber therein, said housing including opposed wall means, a cylindrical pump plunger, means mounting said plunger through one of said wall means for reciprocation within said chamber, inlet passage means including inlet valve means communicating with said chamber, outlet passage means including outlet valve means communicating withsaid chamber, said inlet and outlet passage means including the respective valve means thereof being substantially aligned-on an axis disposed substantially at a right angle to the axis of said plunger, means defining a cylindrical access bore through said other wall means to said chamber, the axis of said bore intersecting the axis of said inlet and outlet passage means and being located a predetermined distance eccentrically from the axis of said plunger toward said inlet passage means whereby the radial clearance between said plunger and said bore adjacent said inlet passage means is a predetermined distance greater than the radial clearance between said plunger and said bore adjacent said outlet passage means, a closure member removably mountable within said bore, arm means secured to said closure member and projecting therefrom into said chamber between said plunger and said inlet passage means, and an arcuately curved surface on said arm means adjacent said plunger and substantially concentric with the latter, wherein said inlet valve means comprises a valve seat within said inlet passage means, an inlet valve member in said inlet passage means and movable between a seated position on said valve seat and an unseated position displaced therefrom toward said pumping chamber, a stop member secured to said valve member and projecting therefrom toward said 9. The pump as defined in claim 8 in which said arcuately curved surface of said arm means defines with the surface of said closure member exposed to said pumping chamber a working area opposite the end of said pump plunger which is less than the area of said bore.

References Ciied by the Examiner UNETED STATES PATENTS 2,146,709 2/39 Bird et a1 103 153 LAURENCE V. EFNER, Primary Examiner.

JOSEPH H. BRANSON, JR., Examiner. 

1. A FLUID PUMP COMPRISING A HOUSING ENCLOSING A PUMPING CHAMBER THEREIN, SAID HOUSING INCLUDING OPPOSED WALL MEANS, PUMP PLUNGER, MEANS MOUNTING SAID PLUNGER THROUGH ONE OF SAID WALL MEANS FOR RECIPROCATION WITHIN SAID CHAMBER, INLET PASSAGE MEANS COMMUNICATING WITH SAID CHAMBER, MEANS DEFINING AN ACCESS BORE THROUGH SAID OTHER WALL MEANS TO SAID CHAMBER, THE AXIS OF SAID BORE BEING LOCATED A PREDETERMINED DISTANCE ECCENTRICALLY FROM THE AXIS OF SAID PLUNGER TOWARD SAID INLET PASSAGE MEANS, A CLOSURE MEMBER REMOVABLY MOUNTABLE WITHIN SAID BORE, ARM MEANS SECURED TO SAID CLOSURE MEMBER AND PROJECTING THEREFROM INTO SAID CHAMBER BETWEEN SAID PLUNGER AND SAID INLET PASSAGE MEANS, THE WIDTH OF SAID ARM MEANS BEING SMALLER THAN SAID INLET PASSAGE MEANS WHEREBY FLUID FLOWING THEREFROM INTO SAID CHAMBER MAY PASS AROUND THE SIDES OF SAID ARM MEANS, AND AN OUTLET PASSAGE MEANS COMMUNICATING WITH SAID PUMPING CHAMBER. 